U.S. patent application number 11/914885 was filed with the patent office on 2008-10-30 for fin unit with elastic attachment system on an underside of a marine apparatus.
Invention is credited to Hugo Heesterman.
Application Number | 20080268730 11/914885 |
Document ID | / |
Family ID | 35636775 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080268730 |
Kind Code |
A1 |
Heesterman; Hugo |
October 30, 2008 |
Fin Unit with Elastic Attachment System on an Underside of a Marine
Apparatus
Abstract
The invention relates to a fin unit (2) with elastic attachment
system on an underside (1) of a marine apparatus, such as a wind
surf, kite surf, fly surf, wakeboard, knee board and particularly a
surfboard. The fin in the mounting thereof is partially made to
self-align in the flow of liquid medium with the aim of avoiding
the hydrodynamic stall caused by the passage of high turbulence
and/or large lateral movements caused by the surfer in extreme
motion. The possibility for self-orientation is due to three
fundamental parameters which are: the type of elasticity of the
attachment system (3-4-5-27), the forward position of the centre of
gravity G towards the leading edge (15) and the form of the root
profile (9) of the fin (2) which has a thickening (7) of the
trailing edge thereof.
Inventors: |
Heesterman; Hugo; (Cadenet,
FR) |
Correspondence
Address: |
Young & Thompson
745 S. 23rd Street., Second Floor
Arlington
VA
22202
US
|
Family ID: |
35636775 |
Appl. No.: |
11/914885 |
Filed: |
May 18, 2006 |
PCT Filed: |
May 18, 2006 |
PCT NO: |
PCT/FR2006/001122 |
371 Date: |
July 7, 2008 |
Current U.S.
Class: |
441/79 |
Current CPC
Class: |
B63B 32/60 20200201;
B63B 32/66 20200201 |
Class at
Publication: |
441/79 |
International
Class: |
B63B 35/79 20060101
B63B035/79 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2005 |
FR |
0504957 |
Claims
1. Removable fin unit with system of fastener on careen of a marine
apparatus (1) such as surfboard, kite surfing, fly surfing, wake
board, knee board, windsurf board or similar, characterised by the
fact that the fin (2) is partially made self directional in its
evolution in fluid environment in order to push back the
hydrodynamic stall caused by the crossing of large turbulences
and/or the strong lateral movements applied by the surfer in
extreme motion, thanks to elastic means of fastening (3-4-5-27)
combined with the forward position of the centre of gravity G and
the form of the profile (7) out of root (9) of the fin (2).
2. Fin unit according to claim 1, characterised in that the form of
the profile of the fin (2) out of root (9) includes a thickening
(7) of the trailing edge (8) of a value equal or lower than the
maximum cross section thickness situated at approximately 25% of
the airfoil cord, the said thickening being built on a height H of
value at least equal to that of the said maximum cross section.
3. Fin unit according to claim 1, characterised in that the means
of fastening units are represented by an insert (5) embedded in the
careen (1) including an elastic matter (4) coating a sleeve (27) in
order to hold at least a tenon (3) out of root (9) of the fin (2),
which assembly allows a partial elastic mobility of the fin around
OZ axis and OX axis.
4. Fin unit according to claim 1, characterised in that the fin (2)
assembled with its means of fastening (3-4-5-27) is brought as to
be able to have angular displacement (Ai and Aj), in the case of
over lift pressure of hydrodynamic nature .DELTA.P, around vertical
axis OZ in yawning Mz and around longitudinal axis OX in rolling
Mx.
5. Fin unit according to claim 1, characterised in that the fin (2)
equipped with tenon (3) is manufactured in such a way that it can
float in the water, that is to say it is composed by a profiled
core (16) made of very light material covered with a skin (17) of
great strength with a leading edge (15) reinforcement by successive
layers, which includes according to the needs a ballast (6) to
adjust the natural frequencies HP, to position the centre of
gravity (G) of the fin close to the root (9) and in front of OZ
axis.
6. Fin unit according to claim 1, characterised in that the fin
(2), in the case of extreme motion or important variations of speed
.DELTA.V at great incidence i, swirl or gust, induce strong
variation of lift .DELTA.P, is self adjustable in incidence by the
fact that the tenon (3)/insert (5) linkage is elastic and that
inertial forces, applied at the centre of gravity G and that the
hydrodynamic forces applied to the action centre O', depending on
the swirling effect from induced drag t.sub.m and root turbulence
t.sub.e, induce yawning moments Mz and rolling moments Mx which
reduce the gust effect by the angular variations Ai and Aj.
7. Fin unit according to claim 3, characterised in that the tenon
(3) is of circular section or rectangular or more or less elliptic,
it can contain at its end a notch or a throttling (10) as to self
position it in its sleeve (27) during its insertion and to be
locked in at its end of travel on an elastic strip (28) or a spring
ring of circlips type (20).
8. Fin unit according to claim 7, characterised in that the fin (2)
is locked in position by a cord (11) fixed at the tenon end or on
the root (9) of the fin, which cord crosses through the thickness
of the board in order to be fixed and tended by a rubber band (12)
located and fixed (13) in a slot (14) practised in the deck of the
board.
9. Fin unit according to claim 7, characterised in that the fin (2)
is attached to the careen (1) by two tenons (3a-3b) inserted in two
mortises (19a-19b) of a non elastic material, each mortise include
inside one or more elastic matter rings (18a-18b) in such a way
that the tenons once introduced are maintained by radial pressure,
at the level of the throttling (10), which allow however a light
elastic displacement of the fin (around axes OX and OZ) in the gap
left between the diameter of the tenons and that of the
mortises.
10. Fin unit according to claim 9, characterised in that the ring
(18a) and the ring (18b) present different elastic deformations
under the same effort, due to the difference of modulus of
elasticity of chosen elastomer and/or with the difference of the
shape of the ring as to position the OZ axis as closer to the front
tenon axis.
11. Fin unit according to claim 9, characterised in that the tenon
(3a-3b) is a part brought back during the manufacture of the fin
(2) whose material used is either metal stainless or titanium, or a
composite, this same tenon includes outside a smooth or ridged or
knurled surface to strengthen the behaviour of the assembly with
the rings (18a-18b) and inside a tubular cavity (22) where there is
a flexible bond (23) of safety connecting one and the other of the
two ends (24-25) of the tenon which in the event of rupture makes
it possible not to lose the fin in the fluid environment.
12. Fin unit according to claim 3, characterised in that the insert
(5) is a kind of very hard composite material cage including
outside the protruding parts (26) for the mooring and the bonding
in the careen (1) and inside other protruding parts (29) to receive
equipments allowing the coupling with at least a tenon (3), the
said insert (5) as to facilitate its installation in the board
includes an angular positioning jig (30) composed of three arms
(31-32a-32b) each one provided with pin (33), the said arm (31) of
length greater than that of arms (32a-32b) is provided with at
least a detachable pin (34) dimensioned and specified with the
angle (.psi.) required.
13. Fin unit according to claim 2, characterised in that the fin
includes at its root (9) an elastic joint (21) filling the
clearances or the gaps between fin and careen.
Description
[0001] The present invention relates to a fin unit with elastic
attachment system on the underside of a marine apparatus, such as a
windsurf board, kite surf, fly surf, wake board, kneeboard and
particularly a surfboard.
[0002] Surfboards are usually equipped with one or with several
fins, more commonly three, fixed at the tail of the board, on the
careen (lower surface of the board). Two methods of fixture exist,
one consists in bonding the fins on the board to make them
interdependent, the other consists in having removable and
interchangeable fins via a box or an insert of fixture incorporated
in the board.
[0003] The traditional fins are generally manufactured using a
plate made up of a multitude of fiberglass layers and resin,
machined or shaped by hand. Then they are made interdependent with
the board by bonding with fiberglass fabrics, unidirectional fiber
and resin.
[0004] This mode of fixture makes it possible to establish at the
root a peripheral fillet to improve the hydrodynamic
characteristics at the base of the fins.
[0005] On the other hand, the presence of fixed fins on the board
during the stages of completion of manufacture involves an
increased duration of this operation and thus the cost of labor, as
well as an increase in the weight and a reduction of the quality of
the board finish surrounding the fins position.
[0006] For these ten last years, many companies launched themselves
in the manufacturing of removable fins systems because they have
multiple advantages, on one hand for surfers whom according to the
type of sport use several type of fins with the same board. On the
other hand, for the board manufacturers who are seeking for speed
of installation of the fins and a less cumbersome and an easier
storage of the boards in the warehouse or during
transportation.
[0007] The boards are most commonly equipped with fins made of
thermoplastic material reinforced with glass powder. They are heavy
and present weak mechanical properties compared with those
traditional fins when they are submitted to a bending stress.
[0008] To obtain the best performances in the wave, during the
various stages of manufacture of a board, the shaper pays a very
detailed attention to the distribution of volume and on its balance
compared to its widest point.
[0009] Despite everything, when the board is equipped with its
fins, the weight of those induces a shift backwards of the centre
of gravity compared to the required optimal position.
[0010] Moreover, disappearance of the fillet, represented by an
amount of resin at the base of the fin, reduces the hydrodynamic
performances while generating in certain configurations an
inopportune stall of the fluid and a loss of control of the board
by the surfer.
[0011] Generally the fins are maintained in position on the board
by a system including one or more screws which fix them in place in
the inserts, as described in the patent FR 2 691 943. That forces
the surfer to use a specific toll in order to mount/dismount the
fins, representing certain difficulties when being on a beach.
[0012] On certain marketed systems, a frequent assembly/disassembly
of the fin or a too high tightening torque of the screw can damage
the threading in the plastic insert, and even deteriorate the
hexagonal head of the screw. This dysfunction can involve a fin
loss or an impossibility of assembling/disassembling it from the
board.
[0013] Others disadvantages have been identified on the existing
systems, such as the possibility of perforating the board fiber
reinforcement during the fin assembly/disassembly because of a
front/back swing of this one. As well as the importance of board
repair after insert's tear off in the case of violent impact, the
shape and the weight of the used insert of fixture and its mode of
embedding in the board.
[0014] Moreover the stiffness of fin/board assembly mounting
causes, in extreme configuration of the evolution practiced by the
surfer, the formation of vortex and vibrations.
[0015] The purpose of the invention is to facilitate the control of
the board by a surfer by having removable fins whose constitution,
shape and assembly on the board, allow to obtain on one hand, an
improvement of the hydrodynamic efficiency by reducing the
formation of vortex/vibrations and on the other hand, to increase
the range of evolution in the waves in a marine environment.
[0016] Thanks to the invention, this goal is reached while making
the fin semi articulated or partially self directional in its fluid
environment evolution, in order to push back the hydrodynamic stall
caused by the crossing of high turbulences and/or by the strong
lateral movements applied by the surfer in extreme motion, thanks
to an elastic means of fastening combined with the forward position
of the centre of gravity G toward the leading edge and the shape of
the root profile of the fin.
[0017] The fin unit with elastic attachment system, in accordance
with the invention, presents a certain number of advantages. Given
that the fin is mounted semi articulated on the board, in addition
that it improves the hydrodynamic performances, it improve also the
service life of the whole assembly with respect to mechanical
shocks or hydrodynamic fluctuations, which are amortised by the
elastic attachment system.
[0018] The invention is described hereafter using examples and
references to joined illustrations, in which:
[0019] FIG. 1 is a side plan view representing the principal
components between fins and careens.
[0020] FIG. 2 is a cross sectional view of drawing 1 showing the
shape of the tenon profile and the insert.
[0021] FIG. 3 illustrates the fin in its work configuration in the
fluid with its associated turbulent flows.
[0022] FIG. 4 is a bottom plan view of the board equipped with
three fins.
[0023] FIG. 5 is a rear view of the board.
[0024] FIG. 6 is a perspective view of the fin/insert assembly.
[0025] FIG. 7 is a rear view of the fin considering the trailing
edge.
[0026] FIG. 8 illustrates different shapes and surface conditions
of tenons.
[0027] FIG. 9 is a perspective view of the insert embedded in the
board.
[0028] FIG. 10 cross sectional view of the insert including its
angular jig fitted in the board.
[0029] FIG. 1 illustrates the whole assembly of the fin (2) on the
careen (1). The fin is equipped with at least one tenon (3) which
is introduced into an insert (5) bonded to the careen (1) including
an elastic matter (4) coating if necessary a sleeve (27) in order
to hold and lock the tenon after its insertion in the housing.
[0030] The mechanical unit thus defined represents the said elastic
means of fastening (3-4-5-27). They bring a partial mobility of the
fin around OZ axis with yawning moment Mz and around OX axis with
rolling moment Mx.
[0031] FIG. 2 represent, according to a cross sectional top view,
the shape of the insert (5), the shape of the tenon (3) and the
shape of the root profile (9) of the fin (2).
[0032] The root profile includes a thickening (7) of the trailing
edge (8) of a value equal or lower than the maximum cross section
thickness situated at approximately 25% of the airfoil cord. This
thickening (7) is built on a height H of value at least equal to
that of the maximum cross section Mc.
[0033] The fin equipped with tenon (3) is manufactured in such a
way that it can float in water. It is composed by a profiled core
(16) made of very light material covered with a skin (17) of great
strength with a leading edge (15) reinforcement by successive
layers. According to the needs, the fin will be fitted with a
ballast (6) for two essential reasons. Namely, the first; in order
to position the fin centre of gravity G close to the root (9) and
in front of OZ axis, the second; as to adjust the Eigen frequencies
Hx and Hz around OX and OZ axis.
[0034] FIG. 3, as a whole, makes it possible to explain how the fin
(2) reacts when it is submitted to more or less laminar and
fluctuating flows. Indeed, for a given speed V and an angle of
incidence i the fin is subjected to a lift P and a drag T whose
centre of action O' is located at the back of OY fastener axis.
[0035] For an angle of incidence close to stall we observe an
amplification of marginal tip vortex t.sub.m, an amplification of
root turbulences t.sub.e and of vibrations.
[0036] These last can be rather destructive when are close to the
natural frequencies HP of the assembly in a turbulent fluid
environment.
[0037] These disadvantages are pushed back while making the fin
reactive and partially self directional while exploiting three
fundamental parameters. To know; [0038] The elastic means of
fastening (3-4-5-27), which according to the grade of elasticity,
determines the importance of the angular displacement .DELTA.i and
.DELTA.j around OX-OY axis. Thus a strong variation of lift
.DELTA.P, caused by a strong variation of speed .DELTA.V, swirl or
gust, will be limited by the rotation of the fin in the way of
angle of attack reduction by considering that action centre O' is
located at the rear of OZ axis. [0039] The form of the root (9)
profile of the fin, whose trailing edge (8) includes a thickening
(7) as shown in FIGS. 1 and 2.
[0040] At a strong variation of lift .DELTA.P, this shape limits
the stall due to the imperfections of fin/careens surfaces junction
and thus limit the displacement of the action centre towards the
leading edge of the fin. [0041] The position of the centre of
gravity G that will be generally adjusted via a ballast (6) so that
the inertial forces bring back to OX and OY axis generate, during
the acceleration of speed .DELTA.V, a rotation of the fin in the
way of incidence reduction.
[0042] It is under these conditions that we can say that the fin,
in the case of in extreme motion or important variations of speed
.DELTA.V at great incidence, is self adjustable in incidence by the
fact that the tenon (3)/insert (5) linkage is elastic and that
inertial forces, applied at the centre of gravity G and that the
hydrodynamic forces applied to the action centre O', induce yawning
moments Mz and rolling moments MX which reduce the gust effect by
the angular variations .DELTA.i and .DELTA.j. The tenon (3),
according to the mountings, can be of circular section or
rectangular or more or less of elliptic section as on the FIG.
2.
[0043] It can contain at its end a notch or a throttling (10) as to
self position it in its sleeve (27) during its insertion and to be
locked in at its end of travel on an elastic strip (28) or a spring
ring of circlips (20) type. The disassembly of the fin operates by
pulling it along OZ axis while pushing on a located point on the
insert as to disengage the elastic strip or the pin from the tenon
notch.
[0044] The fin, in another type of achievement can be locked in
position by a cord (11) fixed at the tenon end or on the root (9)
of the fin. This cord crosses through the thickness of the board in
order to be fixed and tended by a rubber band (12) located and
fixed (13) in a slot (14) practiced in the deck of the board.
[0045] The FIG. 6 represents another type of achievement according
to which the fin (2) is attached to the careen (1) by two tenons
(3a-3b) inserted in two mortises (19a-19b) of a non elastic
material. Each mortise include inside one or more elastic matter
rings (18a-18b) in such a way that the tenons once introduced are
maintained by the radial pressure of the rings which allow however
a light elastic displacement of the fin (around OX and OZ axis) in
the gap left between the diameter of the tenons and that of the
mortises.
[0046] The OZ axis position is between the axis of the tenons
(3a-3b). But in the case where we want to adjust OZ axis as close
as possible to the tenon (3a) axis, it is enough to use rings with
different elastic deformation under the same effort. It is the case
in our assembly where the rings (18a) have a smaller modulus of
elasticity, that is to say harder than the rings (18b). A
difference of size or shape of the ring contained in the mortises
(19) before and back can produce the same effect with an identical
modulus of elasticity.
[0047] FIG. 8 represents the use of various tenons. The tenon is a
part brought back during the manufacture of the fin (2) whose
material used is either a metal stainless or titanium, or a
composite. The tenon has outside a smooth or ridged or knurled
surface to strengthen the behavior of the assembly with the rings
(18a-18b) and inside a tubular cavity (22) where there is a
flexible bond (23) of safety connecting one and the other of the
two ends (24-25) of the tenon which in the event of rupture makes
it possible to not lose the fin in the fluid environment.
[0048] The FIG. 9 represents the insert (5) assembled in the board.
It is a kind of very hard material cage including outside
protruding parts (26) for the mooring and the bonding in the careen
(1). Inside the insert other protruding parts (29) are arranged to
receive equipments allowing the coupling with at least a tenon
(3).
[0049] This assembly, to ensure cost savings by reducing the
duration and facilitating the installation of this one in the
board, includes, FIG. 10, an angular positioning jig (30) composed
of three arms (31-32a-32b) each one provided with a pin (33). The
arm (31) of length greater than that of the arms (32a-32b) is
provided with at least a divisible pin (34) dimensioned and
specified with the angle (.psi.) required.
[0050] This angle (.psi.) is defined by the designer for the
angular positioning of the lateral fins, it defines its angular
position of origin.
[0051] Each ignition pin (34) represents an angular increment
(.DELTA..psi.) comprised between 0.25.degree. and 1.degree., with
regard to the precedent. During the lateral fins installation the
designer must break one or more pins (34) in order to obtain the
angle that he wishes to set for the fin, given by the plane support
of the pin (34) and the pins (33).
[0052] With regard to the installation of the central fin, it is
necessary to break all the pins (34) to obtain an angle of
0.degree., given by the plane support generated by the three pins
(33).
[0053] In order to maintain the contact between the three pins and
the careen surface, the use of a weight on the insert can be
necessary during its installation by bonding in the board.
[0054] Once the inserts are interdependent to the board with the
sought angle, a final grinding is carried out to level the insert
with the careen of the board in order to eliminate all the
protruding members, represented in the hatched part (35) on FIG.
10.
[0055] In the case where the external surface of the equipped
insert does not align itself exactly with that of the careen (1) or
presents asperities, the clearances or the gaps between fin and
careen will be filled by an elastic joint (21) bonded on the careen
or at the base of the fin.
* * * * *